Heretofore, a picture encoding apparatus for encoding input picture data using a method of hierarchy encoding, for example, pyramid encoding has been provided. In this type of picture encoding apparatus, a first hierarchy data being input picture data of high resolution, a second hierarchy data of which its resolution is lower than that of the first hierarchy data, and a third hierarchy data of which its resolution is lower than that of the second hierarchy data, are sequentially and recursively formed. The plurality of hierarchy data are transmitted through one transmitting path being a communicating path or a recording/reproducing route.
In a picture decoding apparatus for decoding this plurality of hierarchy data, all of the plural picture data can be decoded, in addition to this, one of the desired hierarchy data can be selected and decoded in accordance with the resolution of the corresponding television monitor or the like. In this manner, only the desired hierarchy data is decoded out of the plurality of hierarchy data, so that the desired picture data can be obtained with the minimum amount of transmitting data at need.
Here, as shown in FIG. 1, in the hierarchy encoding, a picture encoding apparatus 1 for actualizing for example, four hierarchical-encoding, has decimating filters 2, 3, and 4 of three hierarchies and interpolating filters 5, 6, and 7. The input picture data D1 is passed through the decimating filters 2, 3, and 4 of the respective stages to sequentially form reduced picture data D2, D3, and D4 having a lower resolution, and the reduced picture data D2, D3, and D4 are passed through the interpolating filters 5, 6, and 7 to change the resolutions of those data to that before reducing.
Outputs D2 to D4 of the respective decimating filters 2 to 4 and outputs D5 to D7 of the respective interpolating filters 5 to 7 are input to difference circuits 8, 9, and 10 respectively, in order to generate difference data D8, D9, and D10. As a result, in the picture encoding apparatus 1, the data quantity of hierarchy data and the signal power are reduced. Here, the difference data D8 to D10 and the reduced picture data D4 have the sizes of 1, 1/4, 1/16, and 1/64 respectively in the areas.
The difference data D8 to D10 obtained from the difference circuits 8 to 10 and the reduced picture data D4 obtained from the decimating filter 4, are encoded by respective encoders 11, 12, 13, and 14 and are performed compression processing. As a result, first, second, third, and fourth hierarchy data D11, D12, D13, and D14 which have different resolutions respectively are sent from the respective encoders 11, 12, 13, and 14 to a transmitting path in a predetermined sequence.
Thus transmitted first through fourth hierarchy data D11 through D14 are decoded by a picture decoding apparatus 20 shown in FIG. 2. That is, the first through fourth hierarchy data D11 through D14 are decoded by decoders 21, 22, 23, and 24 respectively, so that the fourth hierarchy data D24 is output from the decoder 24.
Further, in an adding circuit 29, the output of the decoder 23 is added to the interpolating data of the fourth hierarchy data D24 obtained from an interpolating filter 26, to restore the third hierarchy data D23. Similarly, in an adding circuit 30, the output of the decoder 22 is added to the interpolating data of the third hierarchy data D23 obtained from an interpolating filter 27, to restore the second hierarchy data D22. Further, in an adding circuit 31, the output of the decoder 21 is added to the interpolating data of the second hierarchy data D22 obtained from an interpolating filter 28, to restore the first hierarchy data D21.
However, in a picture encoding apparatus realizing the above method of hierarchy encoding, the input picture data is divided into a plurality of hierarchy data and encoding it, hence, the amount of data of the hierarchy component is increased necessarily, as a result, it arises that compression efficiency decreases comparing with the case of using the high-efficiency encoding system in which hierarchy encoding is not used. Further, there is a problem that when improving the compression efficiency, the deterioration of picture quality occurs due to the respective quantizers applied to the hierarchy data.